Discovery of Novel Anti-Biofilm Agents from Soil Dwelling Bacteria

Abstract

Background: ESKAPE pathogens, as classified by the World Health Organization, pose a significant threat to global healthcare due to their resistance to antimicrobial agents. Among these pathogens, Pseudomonas aeruginosa is particularly troublesome due to its ability to form biofilms, which contribute to antimicrobial resistance and complicate treatment strategies. Developing novel antibiofilm agents capable of selectively targeting biofilm structures without affecting planktonic cells is essential for combating these pathogens. Natural products have long been recognized as valuable sources of bioactive compounds with diverse therapeutic properties. Derived from marine organisms, plants and microorganisms, natural products offer a rich reservoir of chemical diversity, making them attractive candidates for drug discovery efforts. In the past few years, there has been a focus on exploring natural products for drug discovery, prompted by the urgency to address antimicrobial resistance and find new solutions for combating biofilm formation. Given their historical significance and proven efficacy, natural products represent a promising avenue for developing new therapies to combat biofilm-associated infections.

Materials: In this study, we investigated the potential of Streptomyces-derived natural products as antibiofilm agents against Pseudomonas aeruginosa biofilms. A Streptomyces strain (BM9) isolated from Beit Meri soil was cultured in a 6L of medium C, resulting in the production of secondary metabolites. These secondary metabolites were tested for their ability to inhibit biofilm formation of a clinical isolate of Pseudomonas aeruginosa (PAN14) without impacting planktonic cell growth. Bio-guided fractionation techniques were employed to isolate bioactive compounds, which were then evaluated for their efficacy in inhibiting biofilm formation and eradicating preformed biofilms using in vitro assays, including the Inhibition of biofilm formation (IF) and Eradication of Preformed Biofilm (PF) assays. The Minimum Biofilm Inhibitory Concentration (MBIC) of the pure compound was determined in addition to its impact on the MBIC of other antibiotics when combined together. Moreover, some physiological, phenotypic and genomic characterization of the bacterial strain BM9 were assessed.

Results: After the liquid-liquid partitioning, Hexane, Chloroform fractions showed significant anti-biofilm activity against Pseudomonas aeruginosa. Subsequent fractionation led to the isolation of a pure compound, exhibiting potent antibiofilm activity with a Minimum Biofilm Inhibitory concentration (MBIC) of 32 µg/mL against preformed biofilms of PAN14 without any effect on planktonic cells. This active compound showed a synergistic effect with two clinically used antibiotics: Gentamicin and Colistin. Furthermore, after the genomic analysis, BM9 was identified as Streptomyces galilaeus. These findings highlight the potential of Streptomyces-derived natural products as effective antibiofilm agents and emphasize the importance of evaluating their safety profiles for future therapeutic development.

Conclusion: The isolated compound from Streptomyces galilaeus BM9 demonstrates promising antibiofilm activity against P. aeruginosa biofilms and warrants further investigation for therapeutic development. This study highlights the potential of natural product-derived compounds as effective antibiofilm agents and underscores the importance of safety evaluation for future clinical applications. Further elucidation of the mechanism of action and additional purification of bioactive compounds from BM9 extract are essential for advancing this research toward clinical translation.